NR PHR design for mmWave deployment

Abstract

New radio (NR) power headroom report (PHR) design for millimeter wave (mmWave) deployment is discussed. The power control process for mmWave may include beam-specific periodic PHR reporting and user equipment (UE)-specific event-trigger PHR reporting. The periodic PHR reporting may either provide a single PHR that includes power headroom information for each of the serving beams, or the UE may be configured to measure and report PHR for different beams in different slots. When reporting a single PHR with power headroom information for multiple serving beams, a beam index may be included in the reserved bits of the PHR. For the event-trigger PHR, the PHR reported based on a detected event trigger may provide power headroom information only for the current serving beam, or for all serving beams.

What is claimed is: 
     
       1. A method of wireless communication, comprising:
 determining, by a user equipment (UE), a beam-specific periodic power headroom report (PHR) in response to expiration of a first reporting timer, wherein the UE receives communications from a serving base station over one or more serving beams beamformed by the serving base station; 
 transmitting, by the UE, the beam-specific periodic PHR to the serving base station; 
 detecting, by the UE, a report triggering event, wherein the report triggering event includes one or more of:
 a pathloss measured on a current serving beam of the one or more serving beams; and 
 a serving beam change at the UE; 
 
 determining, by the UE, a UE-specific trigger PHR in response to the report triggering event and expiration of a second reporting timer; and 
 transmitting, by the UE, the UE-specific trigger PHR to the serving base station. 
 
     
     
       2. The method of  claim 1 ,
 wherein the determining the beam-specific periodic PHR includes:
 measuring a power headroom for each beam of the one or more serving beams; and 
 generating an aggregate PHR including the power headroom for the each beam; 
 
 wherein the transmitting the beam-specific periodic PHR includes transmitting the aggregate PHR. 
 
     
     
       3. The method of  claim 2 , wherein the generating further includes:
 adding a beam identifier to the aggregate PHR, wherein the beam identifier indicates an associated beam of the one or more serving beams corresponding to the power headroom of the aggregate PHR. 
 
     
     
       4. The method of  claim 1 , further including:
 receiving, at the UE, beam reporting configuration from the serving base station, wherein the beam reporting configuration configures the UE to report the beam-specific periodic PHR for each of the one or more serving beams at a different reporting occasion,
 wherein the determining the beam-specific periodic PHR includes determining the beam-specific periodic PHR of a currently-scheduled beam of the one or more serving beams, and 
 wherein the transmitting the beam-specific periodic PHR includes transmitting the beam-specific periodic PHR of the currently-scheduled beam at a currently-scheduled reporting occasion. 
 
 
     
     
       5. The method of  claim 4 , wherein the beam reporting configuration includes one of:
 a different period of the first reporting timer for each of the one or more serving beams; or 
 a different offset to the first reporting timer for each of the one or more serving beams. 
 
     
     
       6. The method of  claim 1 ,
 wherein the determining the UE-specific trigger PHR includes measuring a power headroom for a current serving beam of the one or more serving beams, 
 wherein the UE-specific trigger PHR includes the power headroom for the current serving beam. 
 
     
     
       7. The method of  claim 1 ,
 wherein the determining the UE-specific trigger PHR includes:
 measuring a power headroom for each beam of the one or more serving beams; and 
 generating an aggregate trigger PHR including the power headroom for the each beam; 
 
 wherein the transmitting the UE-specific trigger PHR includes transmitting the aggregate trigger PHR. 
 
     
     
       8. The method of  claim 1 , wherein the second reporting timer and threshold trigger value of the report triggering event are common to the UE and shared across the one or more serving beams, such that a serving beam change does not trigger restart of the second reporting timer. 
     
     
       9. The method of  claim 1 , further including:
 resetting the second reporting timer in response to the serving beam change at the UE. 
 
     
     
       10. The method of  claim 1 , wherein the report triggering event includes a pathloss measured on a current serving beam of the one or more serving beams, wherein a threshold trigger value of the pathloss is at least 15 dB. 
     
     
       11. A method of wireless communication, comprising:
 determining, by a user equipment (UE), a time period since a last beam change of one or more serving beams received at the UE from a serving base station; 
 measuring, by the UE, a pathloss of a beam-specific layer 3 reference signal on a current serving beam in response to the time period exceeding a minimum time threshold; and 
 measuring, by the UE, the pathloss of a beam-specific layer 1 reference signal on the current serving beam in response to the time period being below the minimum time threshold. 
 
     
     
       12. An apparatus configured for wireless communication, comprising:
 means for determining, by a user equipment (UE), a beam-specific periodic power headroom report (PHR) in response to expiration of a first reporting timer, wherein the UE receives communications from a serving base station over one or more serving beams beamformed by the serving base station; 
 means for transmitting, by the UE, the beam-specific periodic PHR to the serving base station; 
 means for detecting, by the UE, a report triggering event, wherein the report triggering event includes one or more of:
 a pathloss measured on a current serving beam of the one or more serving beams; and 
 a serving beam change at the UE; 
 
 means for determining, by the UE, a UE-specific trigger PHR in response to the report triggering event and expiration of a second reporting timer; and 
 means for transmitting, by the UE, the UE-specific trigger PHR to the serving base station. 
 
     
     
       13. The apparatus of  claim 12 ,
 wherein the means for determining the beam-specific periodic PHR includes:
 means for measuring a power headroom for each beam of the one or more serving beams; and 
 means for generating an aggregate PHR including the power headroom for the each beam; 
 
 wherein the means for transmitting the beam-specific periodic PHR includes means for transmitting the aggregate PHR. 
 
     
     
       14. The apparatus of  claim 13 , wherein the means for generating further includes:
 means for adding a beam identifier to the aggregate PHR, wherein the beam identifier indicates an associated beam of the one or more serving beams corresponding to the power headroom of the aggregate PHR. 
 
     
     
       15. The apparatus of  claim 12 , further including:
 means for receiving, at the UE, beam reporting configuration from the serving base station, wherein the beam reporting configuration configures the UE to report the beam-specific periodic PHR for each of the one or more serving beams at a different reporting occasion,
 wherein the means for determining the beam-specific periodic PHR includes means for determining the beam-specific periodic PHR of a currently-scheduled beam of the one or more serving beams, and 
 wherein the means for transmitting the beam-specific periodic PHR includes means for transmitting the beam-specific periodic PHR of the currently-scheduled beam at a currently-scheduled reporting occasion. 
 
 
     
     
       16. The apparatus of  claim 15 , wherein the beam reporting configuration includes one of:
 a different period of the first reporting timer for each of the one or more serving beams; or 
 a different offset to the first reporting timer for each of the one or more serving beams. 
 
     
     
       17. The apparatus of  claim 12 ,
 wherein the means for determining the UE-specific trigger PHR includes means for measuring a power headroom for a current serving beam of the one or more serving beams, 
 wherein the UE-specific trigger PHR includes the power headroom for the current serving beam. 
 
     
     
       18. The apparatus of  claim 12 ,
 wherein the means for determining the UE-specific trigger PHR includes:
 means for measuring a power headroom for each beam of the one or more serving beams; and 
 means for generating an aggregate trigger PHR including the power headroom for the each beam; 
 
 wherein the means for transmitting the UE-specific trigger PHR includes means for transmitting the aggregate trigger PHR. 
 
     
     
       19. The apparatus of  claim 12 , wherein the second reporting timer and threshold trigger value of the report triggering event are common to the UE and shared across the one or more serving beams, such that a serving beam change does not trigger restart of the second reporting timer. 
     
     
       20. The apparatus of  claim 12 , further including:
 means for resetting the second reporting timer in response to the serving beam change at the UE. 
 
     
     
       21. The apparatus of  claim 12 , wherein the report triggering event includes a pathloss measured on a current serving beam of the one or more serving beams, wherein a threshold trigger value of the pathloss is at least 15 dB. 
     
     
       22. An apparatus configured for wireless communication, comprising:
 means for determining, by a user equipment (UE), a time period since a last beam change of one or more serving beams received at the UE from a serving base station; 
 means for measuring, by the UE, a pathloss of a beam-specific layer 3 reference signal on a current serving beam in response to the time period exceeding a minimum time threshold; and means for measuring, by the UE, the pathloss of a beam-specific layer 1 reference signal on the current serving beam in response to the time period being below the minimum time threshold. 
 
     
     
       23. An apparatus for wireless communication, the apparatus comprising:
 at least one processor; and 
 a memory coupled to the at least one processor, wherein the at least one processor is configured to perform operations including:
 determining, by a user equipment (UE), a beam-specific periodic power headroom report (PHR) in response to expiration of a first reporting timer, wherein the UE receives communications from a serving base station over one or more serving beams beamformed by the serving base station; 
 transmitting, by the UE, the beam-specific periodic PHR to the serving base station; 
 detecting, by the UE, a report triggering event, wherein the report triggering event includes one or more of: 
 a pathloss measured on a current serving beam of the one or more serving beams; and 
 a serving beam change at the UE; 
 determining, by the UE, a UE-specific trigger PHR in response to the report triggering event and expiration of a second reporting timer; and 
 
 transmitting, by the UE, the UE-specific trigger PHR to the serving base station. 
 
     
     
       24. The apparatus of  claim 23 ,
 wherein the determining the beam-specific periodic PHR includes:
 measuring a power headroom for each beam of the one or more serving beams; and 
 generating an aggregate PHR including the power headroom for the each beam; 
 
 wherein the transmitting the beam-specific periodic PHR includes transmitting the aggregate PHR. 
 
     
     
       25. The apparatus of  claim 24 , wherein the generating further includes:
 adding a beam identifier to the aggregate PHR, wherein the beam identifier indicates an associated beam of the one or more serving beams corresponding to the power headroom of the aggregate PHR. 
 
     
     
       26. The apparatus of  claim 23 , further including:
 receiving, at the UE, beam reporting configuration from the serving base station, wherein the beam reporting configuration configures the UE to report the beam-specific periodic PHR for each of the one or more serving beams at a different reporting occasion,
 wherein the determining the beam-specific periodic PHR includes determining the beam-specific periodic PHR of a currently-scheduled beam of the one or more serving beams, and 
 wherein the transmitting the beam-specific periodic PHR includes transmitting the beam-specific periodic PHR of the currently-scheduled beam at a currently-scheduled reporting occasion. 
 
 
     
     
       27. The apparatus of  claim 26 , wherein the beam reporting configuration includes one of:
 a different period of the first reporting timer for each of the one or more serving beams; or 
 a different offset to the first reporting timer for each of the one or more serving beams. 
 
     
     
       28. The apparatus of  claim 23 ,
 wherein the determining the UE-specific trigger PHR includes measuring a power headroom for a current serving beam of the one or more serving beams, 
 wherein the UE-specific trigger PHR includes the power headroom for the current serving beam. 
 
     
     
       29. The apparatus of  claim 23 ,
 wherein the determining the UE-specific trigger PHR includes:
 measuring a power headroom for each beam of the one or more serving beams; and 
 generating an aggregate trigger PHR including the power headroom for the each beam; 
 
 wherein the transmitting the UE-specific trigger PHR includes transmitting the aggregate trigger PHR. 
 
     
     
       30. The apparatus of  claim 23 , wherein the second reporting timer and threshold trigger value of the report triggering event are common to the UE and shared across the one or more serving beams, such that a serving beam change does not trigger restart of the second reporting timer. 
     
     
       31. The apparatus of  claim 23 , further including:
 resetting the second reporting timer in response to the serving beam change at the UE. 
 
     
     
       32. The apparatus of  claim 23 , wherein the report triggering event includes a pathloss measured on a current serving beam of the one or more serving beams, wherein a threshold trigger value of the pathloss is at least 15 dB. 
     
     
       33. An apparatus for wireless communication, the apparatus comprising:
 at least one processor; and
 a memory coupled to the at least one processor, wherein the at least one processor is configured to perform operations including:
 determining, by a user equipment (UE), a time period since a last beam change of one or more serving beams received at the UE from a serving base station; 
 measuring, by the UE, a pathloss of a beam-specific layer 3 reference signal on a current serving beam in response to the time period exceeding a minimum time threshold; and 
 measuring, by the UE, the pathloss of a beam-specific layer 1 reference signal on the current serving beam in response to the time period being below the minimum time threshold.